The invention relates to a shaped flange for connecting air duct segments.
In the production of ventilating and air conditioning ducts, air duct segments are connected to one another via shaped flanges. The shaped flanges are cut to size and connected to each other by means of corner angles. The shaped flanges are then drawn onto the air duct segments. The two portions of each shaped flange which are perpendicular to the front wall of the respective flange receive, that is, overlie and underlie, the associated wall of the air duct segment.
Among other criteria, it is important to assure that a seal exists between the sheet material wall of the air duct segment and the portion of the shaped flange which underlies this wall.
The West German Pat. No. 32 03 204 describes an arrangement of the type under consideration for connecting air duct elements which, at their abutting edges, are provided with shaped flanges defining receiving spaces for angled corner members. Here, it has been attempted to solve the sealing problem by providing a sealing ledge in that wall zone of the shaped flange which, during use, is parallel to the plane of, and faces away from, the seam. The desired sealing effect can, however, be obtained only if the sealing ledge bears against the front wall of the shaped flange in an airtight manner. This is impossible on production grounds.
The West German Offenlegungsschrift No. 23 53 625, which describes a butt joint different from the type under consideration for duct sections of sheet material, discloses a shaped flange which is placed on the edge of the respective duct side wall and secured by spot welds. The duct side walls are thus not inserted in corresponding receiving spaces of the shaped flange.
The legs of the shaped flange extending perpendicular to the duct walls are provided with sealing strips which are clamped by rolling. The sealing effect in this construction accordingly depends upon the installation of the duct segments and upon the clamping force of the clamping element which holds the shaped flanges together. Furthermore, the seal can be cut by the free front edges of the duct segments during assembly of the duct segments. In practice, precision installation of the duct segments is as good as impossible since tolerances of more than 5 mm are the rule.